The present invention pertains to a shifting device for an automatic transmission with a shifting mechanism mounted in a housing pivotably around an axis within at least one shift gate. The shifting mechanism detects the shift signals electrically, electromagnetically or optically and transmits them. The shifting mechanism has a locking device which is guided with the gearshift lever along a contour of a gate. The contour is associated with the shift positions (P, R, N, D, . . . ).
Such shifting devices for the powerless transmission of shift commands to an automatic transmission of a motor vehicle have a gearshift lever mounted pivotably around at least one axis in a housing in at least one shift gate. The gearshift lever detects the shifting signals electrically, electromagnetically or optically and transmits them correspondingly. A locking device, which is guided with the gearshift lever along a contour of a shifting gate, which contour is associated with one of the shift positions (P, R, N, D, . . . ), makes possible the simulation of the individual shift positions for the driver of the vehicle in order to impart a xe2x80x9cfeeling of shiftingxe2x80x9d to the driver. Such a shifting device has been known, e.g., from the patent application DE 197 56 034 A1.
These prior-art, so-called xe2x80x9cshift by wirexe2x80x9d shifting devices transmit the shift commands mostly to an electronic control device, which transmits the corresponding shift command to the automatic transmission as a function of optionally preselected parameters when this is permitted by the driving conditions of the vehicle. Thus, there is a permanent set point-actual value comparison. The driver of the vehicle can theoretically select another, actually unacceptable shift position with the gearshift lever during travel without this shift position being immediately transmitted to the transmission, because the permissible parameters, e.g., the speed of the vehicle, do not agree with the gear selected.
Thus, it would also be conceivable that the reverse gear is selected even though the vehicle is moving forward. However, the automatic transmission would not shift. However, if the preset parameters are reached during travel, i.e., e.g., the speed drops below a certain limit value, the control device transmits the reverse gear selected before by mistake to the automatic transmission and the corresponding gear is engaged. This may lead to accidents, e.g., in intersections.
The basic technical object of the present invention is to provide a shifting device which effectively avoids shifting errors.
According to the invention, a shifting device for an automatic transmission is provided with a shifting mechanism, which is mounted in a housing pivotably around a axis within at least one shift gate. The shift mechanism detects the shift signals electrically, electromagnetically or optically and transmits them. The shift mechanism has a locking device, which is guided with the gearshift lever along a contour of a gate. The contour is associated with the shift positions (P, R, N, D, . . . ). A device is controlled as a function of the speed and can be pivoted between at least two positions (active/inactive) around an axis and can be pivoted against the locking device in at least one shift position, so that the gearshift lever remains in the preselected shift position or is automatically returned into that shift position.
Accidental shifting errors can be effectively prevented from occurring with a shifting device with a device, which is controlled in a speed-dependent manner and can be pivoted between at least two positions (active/inactive) around an axis and can be pivoted against the locking device in at least one shift position. This allows the gearshift lever to remain in the preselected shift position or it is automatically returned into that shift position. The shifting device has a very simple design and the device can likewise be switched or controlled via the central control device.
According to another embodiment of the present invention, a ramp lever pivotable around an axis is used as the device pivotable between at least two positions (active/inactive), the ramp lever assuming a position that prevents the accidental selection of the reverse gear during travel in at least one forward gear of the gearshift lever.
This ramp lever may have a contact surface rising in a ramp-like manner on its side facing the locking device.
The ramp lever is preferably coupled with an adjusting member, which may be a linkage, an electromagnet or a hydraulically or pneumatically acting adjusting device.
The adjusting member has an adjusting element, which has variable length, can be pivoted around a mounting point and is coupled with the ramp lever at a spaced location from its axis, so that a change in the length of the adjusting element exerts a leverage acting on the ramp lever, so that the ramp lever can be pivoted between an activated position and an inactivated position.
Corresponding to a variant of the present invention, the ramp lever assumes an activated position which prevents a shifting error when the speed of the vehicle is higher than a preset limit value of, e.g., 5 km/sec and the forward gear (D) is selected.
The gearshift lever can thus be pivoted only between the shift positions xe2x80x9cNxe2x80x9d and xe2x80x9cDxe2x80x9d with the ramp lever activated and the locking device is moved along the rising contact surface of the locking lever with increasing force applied during a movement in the direction of a shifting error, i.e., e.g., from a forward gear into the shift position xe2x80x9cR,xe2x80x9d so that the gearshift lever will automatically assume the neutral position xe2x80x9cNxe2x80x9d or the gear xe2x80x9cDxe2x80x9d selected previously after it has been released by the driver of the vehicle.
On the side facing the locking device, the ramp lever can have a contour corresponding to a shifting gate at least in some sections. This has the advantage that a changeover between the shift positions xe2x80x9cDxe2x80x9d and xe2x80x9cNxe2x80x9d is possible with the ramp lever activated and only the selection of the reverse gear is prevented.
Corresponding to another embodiment according to the present invention, the locking device may include a leaf spring fastened to the gearshift lever, at the free end of which a mount with a contour roller mounted freely rotatably in it is present, which rolls on the contour of the shifting gate. The contour of the shifting gate may have a wave-shaped design in the known manner, with each wave valley corresponding to one shift position (P, R, N, D, . . . ).
The features of the present invention which were mentioned above and will be explained below can, of course, be used not only in the particular combination indicated but in other combinations as well, additionally or alone, without going beyond the scope of the present invention.